1. Field of the Invention
The present invention relates to a closure system for cylindrical plastics casings.
A cylindrical plastics casing is understood as meaning, for example, the casing of a plastics immersion pump which substantially has a cylindrical casing wall and a casing cover. In the context of the invention, however, it may also be another cylindrical casing which in particular must be closed in a secure and pressure-resistant manner over a relatively long period.
2. Description of the Prior Art
Today, various closure systems are used for closing the pump casing of a plastics immersion pump. In particular, the use of at least one locking ring is known. This is mounted on the substantially circular casing cover, which in turn rests on an annular stop of the casing wall and closes the pump casing at the end. In the case of this known closure system, the cylindrical casing wall is additionally provided, on its end section projecting beyond the fastening region of the casing cover, with an all-round annular groove into which said securing ring is inserted.
Particularly in the case of plastics immersion pumps, the problem arises where the casing is to be closed with the securing ring in such a way that the casing cover is not forced out of the pump casing by the delivery pressure of the pump even at maximum operating pressure, at maximum operating temperature and also after a decline in the clamping force of the locking ring. This is prevented in the case of some known immersion pumps by a plurality of ribs which are arranged in the manner of spokes on the outside of the casing cover and are dimensioned in such a way that they are flush with the locking ring at the end face and thus permit fixing of the locking ring by means of plastics screws inserted into the ribs. The forcing of the locking ring out of the groove in the casing wall and hence separation of the casing cover is thus prevented in this case by fixing means mounted on the outside. However, this known solution is insufficient and unsatisfactory since the small threads in the ribs and the plastics screws are susceptible to faults and their installation is time-consuming.
It is the object of the present invention to provide a novel closure system which has a locking ring detachable from said system and does not have the disadvantages of the closure systems described above. In particular, the function of the closure system is to be improved compared with the known system in such a way that the locking ring is secured both radially and axially in the inserted and assembled state.
This object is achieved by a closure system for cylindrical plastics casings, in particular pump casings of plastics immersion pumps, which system has a substantially cylindrical casing wall, a detachable casing cover and a locking ring which is intended for closing the casing cover and, in the mounted state, is arranged on the outside of the casing cover and is inserted into an annular groove in the casing wall,
the casing cover being provided on its outside with at least two ribs which are arranged in a spoke-like manner and each have an outer projection and with this each expose a groove radially accessible from the outside,
the locking ring being provided with the same number of radially inward projecting tabs as ribs possessed by the casing cover, and being capable of being brought into a locking position by rotation on the casing cover, and
the tabs being dimensioned and arranged in such a way that, in the locking position, they are each inserted with a tight fit into a groove of the ribs arranged on the end face of the casing cover.
As in the case of the known systems, the closure system according to the invention is formed from the casing cover and the locking ring. However, it is distinguished therefrom substantially in that, in the mounted state, i.e. in the closed state of the casing cover, the locking ring engages both the casing wall and the ribs of the casing cover.
According to the invention, the casing cover is provided with at least two ribs which are arranged in a spoke-like manner and each have an outer projection and with this each expose a groove radially accessible from the outside. In comparison, the locking ring has two ends which are adjacent to one another and can be pressed against one another for insertion into the groove of the casing wall, and said locking ring is provided with the same number of radially inward projecting tabs as the ribs possessed by the casing cover. According to the invention, the tabs of the locking ring are dimensioned and arranged in such a way that, in the mounted state, i.e. closed state of the casing cover, they are each inserted with a tight fit into a groove of the ribs arranged at the end face of the casing cover.
In preferred embodiments of the invention, the casing cover has six, eight or twelve ribs arranged at regular intervals radially symmetrically to one another and the locking ring likewise has six, eight or twelve matching tabs. Furthermore, the width of the tabs is preferably about ⅔ of the outermost radial spacing of the ribs.